The disclosure relates to display devices and more particularly relates to bit slice addressing of Liquid Crystal Display (LCD) and multi bit-slicing of Active Matrix LCD (AMLCD).
Pixels are interconnected such that each pixel can be addressed uniquely with a row and a column electrode in LCD. Therefore, LCD has as many digital to analog converters (DACs) as the number of columns in the display to control intensity of pixels whereas just three DACs are adequate to control the intensity of pixels in CRT. It is desirable to have a mechanism which is similar to z-modulation of CRT to control intensity of pixels in flat panel displays.
Bit Slice Addressing (BSA) proposed by T. N. Ruckmongathan in “An addressing technique to drive blue phase LCDs,” Publisher: Society for Information Display, IDW'10, Proceedings of the international display workshop, p 607, 2010, has the elegance and simplicity of z-modulation of CRT. BSA is based on using fast responding LCD as a dynamic mask to display the bit planes of images sequentially, while simultaneously controlling the intensity of backlight to be proportional to the bit-weight of the bit frame that is displayed. When bit frames of images are displayed in a rapid manner it is perceived as the original image by humans due to the integrating nature of human vision.
BSA replaces the complex DACs (8 to 10-bits) in data drivers with simple level shifters that are equivalent to 1-bit DACs. Power consumption of backlight can be reduced by switching “OFF” parts of backlight that illuminate clusters of pixels that are driven to “OFF” state in bit-plane frames. About 20 to 40% reduction in backlight power can be achieved even in images with good contrast and brightness by selective switching of backlight. A viewing angle characteristic that is independent of gray scales and consequently color purity of images, elimination of motion blur, large voltage margin for switching pixels etc., are some additional advantages of BSA. Ferroelectric LCD, a passive matrix type bi-stable display and active matrix type blue phase LCD can be driven with BSA. The main stream active matrix LCDs use either IPS (in-plane switching) or VAN (vertically aligned nematic) mode with response times of a few milliseconds. State of the art IPS and VAN LCDs are marginally slow for bit slice addressing. Multi-Bit Slice Addressing (MBSA) is proposed to drive AMLCDs with response times of a few milliseconds it is a trade-off between response time of the panel and hardware complexity of data drivers.